1. Field of the Invention
The present invention relates to a method for laminating an object to be laminated, using a thermoplastic resin solution (transparent thermoplastic ink), and particularly to a laminating method, which involves laminating a sheet, as a medium, using a thermoplastic resin solution, and transferring the resultant laminate on the lamination sheet onto an object to be laminated, without directly laminating the object using the thermoplastic resin solution, and the lamination sheet which is used in the laminating method. More particularly, the present invention relates to a laminating method, in which a released sheet such as an overlay paper, release paper or synthetic resin film is laminated using a thermoplastic resin solution (transparent thermoplastic ink) obtained by dissolving a polyolefine-based synthetic resin such as polyethylene, polypropylene, PVC or polystyrene in an organic solvent, thereby forming a lamination sheet (a medium), and the resultant laminate on the lamination sheet is then transferred onto an object to be laminated, and the lamination sheet which is used in the laminating method.
2. Description of the Prior Art
Laminating methods are well known which are used to coat a thermoplastic resin solution over an object to be laminated, in the form of a thin film, in order to obtain anti-moisture, seal maintenance and printed surface protection purposes of the object. In conventional laminating methods, a thermoplastic resin film made of a polyolefine-based thermoplastic resin such as polyethylene, polypropylene and PVC or a polyester film is thermally fused onto both surfaces of an object (a printed sheet), such as a resident card or other identification cards, to be laminated, in order to prevent a forgery of the object or to protect the content of the object. The resultant films on the object are then cut along a line spaced apart from each edge of the object by a desired distance, so as to produce a laminated product of a desired size. Such methods have also been used for large-size old documents, deterioratable important documents, and other printed paper.
However, the conventional laminating methods have drawbacks of a rough appearance and a large consumption of the synthetic resin material due to an excessive thickness of the synthetic resin film. Furthermore, the synthetic resin film exhibits a degraded adhesion to the surface of the object. As a result, the film may be easily undone from the surface of the object. In addition, the characters or figures printed on the object may be indistinctly viewed because their images are viewed in a refracted state.
Where large-size printed matter is laminated in accordance with the above mentioned conventional methods, a synthetic resin film having a large size is used. Due to the large size, however, the synthetic resin may have folded or wrinkled portions. Furthermore, a severe looseness of the film may occur due to an entrapment of air between the film and object. In addition, there is an inconvenience in that after the lamination, the laminate should be cut along a line spaced apart from each edge of the object by a certain distance.
In order to solve the above mentioned problems, a roller coating method has also been proposed which utilizes a lamination of a synthetic resin solution using a coating roller. For example, this method has been used to obtain anti-moisture and seal maintenance characteristics of paper bags containing a dose of sugar or medicine, thereby preventing a physical or chemical degradation in the quality of the content due to a moisture absorption of the content or a contact of the content with air. This method has also been used to protect the surface of printed matter.
In accordance with this method, a printed or unprinted object, which is wound around a wind roller in the whole uncut paper state, is continuously coated at one or both surfaces thereof with a synthetic resin solution using one or more coating rollers while being fed by guide rollers. The coated object is then dried. Thus, a lamination of the object is achieved.
The synthetic resin solution consists of a synthetic resin dissolved in an organic solvent. Where the coating process is carried out for a printed surface, the organic solvent of the synthetic resin solution comes into contact with the print ink of the characters or figures printed on the object. As a result, the print ink may be dissolved and dispersed. This results in a contamination of the printed matter, thereby causing a degradation in the print quality. Moreover, an offensive smell is generated during an evaporation of the organic solvent. In addition, such a generation of the organic solvent gas becomes severe because the synthetic resin solution is used in a heated state. This may result in severe damage to the human body.
For this reason, the laminating method using a synthetic resin solution has been used only in factories in a mass-production fashion. In other words, coating a synthetic resin solution over an object using a small-scale laminator (a thermal fusing machine) in homes or offices is generally avoided.